Logs a user out of an existing SSO session - this makes the user no longer logged into any of the SSO-based applications.
There is no response on success. A ValidationError is raised if input is invalid, for instance, if UST does not exist.
logout(self, cid, ust, current_app, remote_addr)
cid: Correlation ID used by audit log
ust: User session token to log out by
current_app: Name of application the user is using to log out from SSO
remote_addr: User's remote address